linux-kernel - Re: [PATCH v2] rtc: ds1307: provide an indication that the watchdog has fired

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Message-ID: <20200727031541.GA53573@roeck-us.net>
Date:   Sun, 26 Jul 2020 20:15:41 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        linux-rtc@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rtc: ds1307: provide an indication that the watchdog
 has fired

On Mon, Jul 27, 2020 at 11:13:06AM +1200, Chris Packham wrote:
> There's not much feedback when the ds1388 watchdog fires. Generally it
> yanks on the reset line and the board reboots. Capture the fact that the
> watchdog has fired in the past so that userspace can retrieve it via
> WDIOC_GETBOOTSTATUS. This should help distinguish a watchdog triggered
> reset from a power interruption.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> ---
> Changes in v2:
> - Set bootstatus to WDIOF_CARDRESET and let userspace decide what to do with
>   the information.
> 
>  drivers/rtc/rtc-ds1307.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 49702942bb08..209736db510d 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -868,6 +868,14 @@ static int ds1388_wdt_start(struct watchdog_device *wdt_dev)
>  	struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
>  	u8 regs[2];
>  	int ret;
> +	int val;
> +
> +	ret = regmap_read(ds1307->regmap, DS1388_REG_FLAG, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val & DS1388_BIT_WF)
> +		wdt_dev->bootstatus = WDIOF_CARDRESET;

This should be done during probe, ie in ds1307_wdt_register().

Guenter

>  
>  	ret = regmap_update_bits(ds1307->regmap, DS1388_REG_FLAG,
>  				 DS1388_BIT_WF, 0);
> -- 
> 2.27.0
>